Method and apparatus for controlled pumping of liquid mercury

ABSTRACT

A controllable flow of liquid mercury is discharged into a delivery conduit. First and second electrodes are positioned in the conduit in the liquid mercury therein. The conduit between the electrodes is electrically insulative. A bubble of electrolyte is positioned between the electrodes. An electrolysis current source is connected to the electrodes and regulated in accordance with the amount of mercury desired to be delivered by this delivery conduit. this electrolysis current electrolyzes mercury across the electrolyte from the mercury source toward the discharge end of the delivery conduit. Detection means detect the position of the electrolyte bubble and regulates the controllable flow of liquid mercury to maintain the electrolyte bubble in a substantially fixed position in the delivery conduit. Thus, the amount of mercury delivered out of the delivery conduit is equal to the amount of mercury electrolyzed across the electrolyte.

United States Patent 1 [72] Inventor Harry J. King Canoga Park, Calif. [21] Appl. No. 687,020 [22] Filed Nov. 30, 1967 [45] Patented Aug. 17, 1971 [73] Assignee Hughes Aircraft Company Culver City, Calif.

[54] METHOD AND APPARATUS FOR CONTROLLED PUMPING OF'LIQUID MERCURY 10 Claims, 1 Drawing Fig.

[52] US. Cl 417/48, 137/2 [51] Int. Cl GOln 27/42, Fl7d H00 [50] Field oiSearch 356/181;

Pu mp 3,255,413 6/1966 Marwell 324/94 3,321,635 5/1967 Jacobs 324/94 3,427,539 2/1969 Mann 324/94 Primary Examiner-William L. Freeh Attorneys-James K. Haskell and Allen A. Dicke,Jr.

ABSTRACT: A controllable flow of liquid mercury is discharged into a delivery conduit. First and second electrodes are positioned in the conduit in the liquid mercury therein. The conduit between the electrodes is electrically insulative. A bubble of electrolyte is positioned between the electrodes. An electrolysis current source is connected to the electrodes and regulated in accordance with the amount of mercury desired to be delivered by this delivery conduit. this electrolysis current electrolyzes mercury across the electrolyte from the mercury source toward the discharge end of the delivery conduit. Detection means. detect the position of the electrolyte bubble and regulates the controllable flow of liquid mercury to maintain the electrolyte bubble in a substantially fixed position in the delivery conduit. Thus, the amount of mercury delivered out of the delivery conduit is equal to the amount of mercury electrolyzed across the electrolyte.

PATVENTED mm 1 I97! 3,600,104

11 [III] 11/ Harry J. King, INVENTOR.

Allen A. Dicke, Jr.,

AGENT METHOD AND APPARATUS FOR CONTROLLED PUMPING OF LIQUID MERCURY BACKGROUND This invention is directed to a method and apparatus for the controlled pumping of liquid mercury, particularly at very low rates.

The pumping of liquid is a very old art, and in most cases the advances in the art of pumping have been directed to the pumping of greater quantities of liquid, or the pumping at higher discharge pressures. On the other hand, while there has been some concern about the accurate pumping of small quantities of liquid, little improvement has been accomplished in recent years except through the improved seals in mechanical pumps. Even with the progress that has been made, mechanical pumps or flow control valves have been unable to accomplish proper control when the desired flow rate is very low.

In the pumping of liquid mercury, the metallic character of the liquid pumped has been recognized by \Vilfried O. Eckhardt in his Pat. application Ser. No. 687,004 filed Nov.

30, i967 entitled Liquid Mercury Flow Control and Measuring System." This prior invention recognizes that the electrolysis of mercury through an electrolyte can deliver liquid mercury at very low flow rates. However, this prior invention is limited by the fact that the maximum delivery pressure is determined by a mercury column and it is not capable of delivering at the higher pressures which are possible with pressurized mercury vessels or mechanical pumps.

SUMMARY In the summary, this invention is directed to a system wherein a controllable supply of liquid mercury delivers mercury through a delivery conduit and particularly to the control of the controllable supply. The delivery conduit has an electrolyte bubble therein, with the electrolyte being of such nature that mercury can be electrolyzed across the bubble in the direction of mercury delivery. Suitable electrolyzing electrodes and power supply are provided, with the amount of electrolysis current determining the amount of mercury delivered. So long as the electrolyte bubble is maintained in a constant position, the amount of mercury delivered is equal to the amount electrolyzed across the bubble. Electrolyte position detecting means controls the controllable mercury supply to maintain the electrolyte in a fixed position to accomplish this result. Thus, the method and apparatus for controlling the pumping of liquid mercury is especially suited for the delivery of liquid mercury at very low and accurately controlled flow rates.

Accordingly, it is an object of this invention to provide a method and apparatus for controlling the supply of liquid mer cury wherein mercury is delivered at low and carefully controlled feed rates. It is another object to provide a method and apparatus in which the liquid mercury can be delivered from its delivery conduit at low and carefully controlled feed rates and at a substantial pressure, should a substantial pressure be required at the discharge point. It is a further object of this invention to provide a delivery system for liquid mercury wherein liquid mercury and liquid electrolyte are in interface relationship so that the mercury can be electrolyzed across the electrolyte. It is still another object of this invention to provide a liquid mercury delivery system wherein the mercury is primarily moved by a source of liquid mercury under pressure having control of the flow of liquid mercury and the control is established without the need for a mercury head so that mercury can be delivered to a discharge point at accurate rates independent of changing in the magnitude or direction of the local gravitational field. Other objects and advantages of this invention will become apparent from the study of the following portion of this specification, the claims and the attached drawings.

DESCRIPTION OF THE DRAWING The single FIGURE of the drawing shows the liquid mercury delivery conduit in longitudinal section and shows the associated equipment for controlling the flow of liquid mercury through the delivery conduit in schematic form.

DESCRIPTION The drawing illustrates the apparatus for controlled pump ing of liquid mercury, which is generally identified at 10. Delivery conduit 12 has an input end 14 to which is connected pump 16. Pump 16 is a pump in the broad sense of the term and includes any device which supplies liquid mercury at suitable pressure and controls its flow. Under these conditions pump 16 can be a pressurized mercury vessel equipped with a controllable metering outlet valve. On the other hand, it can be an electromagnetic pump or a simple mechanical pump with bypass flow control, or the like. In any event, the amount of mercury delivered by pump 16 into the input end 14 of delivery conduit 12 is controlled by the signal in line 18. Pump power, if required is supplied by line 20.

Delivery conduit 12 has a control section 22. Control section 22 contains electrolyte bubble 24. The control section is electrically insulative along its length, is not wettable by mercury 26 in the delivery conduit, is wetted by electrolyte bubble 24, and is of such nature that the position of electrolyte bubble 24 is detectable. Glass is a suitable material for control section 22, especially when optical means is used to detect the position of electrolyte bubble 24. The control section 22 extends from electrode 28 to electrode 30. Beyond the control section, delivery conduit 12 has a discharge section 32 which is connected to the point of use of the liquid mercury. Delivery conduit 12 is filled with liquid with a pump column 34 extending between pump 16 and electrolyte bubble 24 and measured column 36 which extends from the electrolyte bubble 24 through the discharge section 32 to the point of mercury use.

Regulatable current supply 38 is connected to electrodes 28 and 30 to cause electrolysis of mercury from pumped column 34 to measured column 36. The amount of current supplied by the current supply 38 is set in accordance with the desired rate of mercury delivery by the delivery conduit. Faradays law establishes the linear relationship between the amount of mercury delivered across the electrolyte and the electrolysis current. Thus, with the establishment of a particular electrolysis current, a particular rate of mercury flow across the electrolyte is established. By holding the electrolyte bubble 24 stationary along the length of delivery conduit 12, the amount of mercury electrolyzed thereacross is delivered out of the discharge section of the conduit.

Any convenient type of electrolyte bubble position detecting means can be used to regulate the amount of mercury delivered by pump 16 into the input end of delivery conduit 12. Inductive or capacitive means could be used, but optical means is preferred and is illustrated in the FIGURE. Light source 40 directs collimated light through the control section 22 of the delivery conduit and light passing through the fairly transparent electrolyte 24 falls upon sensors 42 and 44 which may be, for instance, EG&G Inc. photodiode bicell SOD-444- 2. The varying intensity of light from source 40 passing through electrolyte bubble 24 onto the two sensors 42 and 44 thus detects the position of the electrolyte bubble.

If the bubble moves to the right, as is seen in the FIGURE, the light falling upon sensor 44 increases and that falling upon sensor decreases. Sensors 42 and 44 are connected to pump controller 46 which is in turn connected by line 18 to control the delivery of liquid mercury by pump 16 into the delivery conduit. In the illustrated case, when bubble 24 moves to the right, the output of pump 16 is too great and the signal of more light falling upon sensor 44 decreases pump output. Similarly, if the bubble 24 is farther to the left in the delivery conduit, more light falls on sensor 42 and less on sensor 44 to cause pump controller 46 to increase pump output. The increased pump output continues until bubble 24 is repositioned so that the amount of light falling upon the sensors 42 and 44 is substantially equal. The system including the sensors, pump controller 46 and the controllability of pump 16 is continuously variable so that electrolyte bubble 24 is maintained closely near the desired fixed position.

A number of different electrolytes can be used to form electrolyte bubble 24. The electrolyte must be capable of electrolyzing mercury, it must wet the interior surface of control section 22 to prevent a short circuit of mercury along the wall of control section 22, and in the instance illustrated must be fairly transparent. However, with different position sensors, transparency will not necessarily be required. Furthermore, different electrolytes have different electrolytic capabilities before they break down due to excess current. Thus, the electrolyte may be chosen with the amount of desired mercury flow rate in mind. A suitable electrolyte is mercury iodide in iodide solution. The table below illustrates practical limits on the preferred electrolyte.

Table A Preferred Kl 750 grams Hgl 225 grams H,O 1000 cc.

Q (Coulombs amp sec)(atomic wt) Mass flow (grams/hr) 96520 (valence) Using the above assumptions and the data for mercury:

Thus, the delivery rate in the illustrative example is 0.0018 grams per hour of mercury. This rate is independent of tube diameter and dependent only upon the current flow. Current can be decreased to reduce the delivery rate, and can be increased up to the limit of the stability of the electrolyte. increases in the tube diameter can be made to maintain electrolyte current density at a reasonable level up to the point where the electrolyte can no longer separate the mercury columns. This is a function of the surface activity of the electrolyte with respect to the material of the control section 22 of delivery conduit 12.

This invention having been described in its preferred embodiment, it is clear that it is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.

What I claim is:

1. An apparatus for the controlled pumping of liquid mercu- Mass flow (grams/hr)= =0.0018

ry, said apparatus comprising:

a source of liquid mercury, a delivery conduit connected to said source of liquid mercury, the improvement compristrodes; and a sensor positioned ad acent said delivery conduit between said fust and second electrodes to sense the position of an electrolyte within said delivery conduit between said electrodes, said sensor being connected to said flow control means so that the rate of mercury flow into said conduit is controlled by said sensing means and said sensing means is controlled by the position of electrolyte within said delivery conduit.

2. The apparatus of claim 1 wherein first and second mercury columns are positioned within said delivery conduit and an electrolyte is positioned between said mercury columns in said delivery conduit, said electrolyte and said mercury columns being in liquid-to-liquid interface engagement.

3. The apparatus of claim 2 wherein said delivery tube is unwettable by said mercury and is wetted by said electrolyte so that said electrolyte maintains said mercury columns electrically separated except through said electrolyte.

4. The apparatus of claim 3 wherein said electrolyte contains mercury ions in electrolyte solution.

5. The apparatus of claim 1 wherein at least a portion of said delivery tube is substantially transparent and first and second columns of liquid mercury in said delivery tube are separated by a substantially transparent mercury plating electrolyte, said electrolyte being positioned between said electrodes.

6. The apparatus of claim 5 wherein said sensor comprises a light source arranged to direct light through said delivery tube and a light sensor positioned to receive light passing from said light source through said delivery tube.

7. The apparatus of claim 6 wherein said light source is a collimated light source and said sensor comprises first and second optical sensors positioned adjacent each other in a direction axial of said tube.

8. A process for the controlled pumping of liquid mercury comprising the steps of:

controllably admitting liquid mercury into a delivery tube so as to substantially fill the delivery tube;

electrolyzing mercury across a mercury electrolyzing electrolyte which is positioned within the tube and separates the mercury column within the tube; and

controlling the position of the electrolyte within the tube by controlling the admission of the liquid mercury into the tube.

9. The process of claim 8 wherein said controlling step comprises:

sensing the position of the electrolyte within the conduit;

and

controlling the admission of liquid mercury into the conduit by the sensed position of the electrolyte.

10. The process of claim 9 wherein said sensing step comprises optically sensing the position of the electrolyte along the length of the conduit. 

1. An apparatus for the controlled pumping of liquid mercury, said apparatus comprising: a source of liquid mercury, a delivery conduit connected to said source of liquid mercury, the improvement comprising: flow control means connected to said delivery conduit to control the rate of flow of liquid mercury from said source into said delivery conduit; first and second electrodes positioned within said delivery conduit and spaced along the length of said delivery conduit for passing electrolysis current between said electrodes; and a sensor positioned adjacent said delivery conduit between said first and second electrodes to sense the position of an electrolyte within said delivery conduit between said electrodes, said sensor being connected to said flow control means so that the rate of mercury flow into said conduit is controlled by said sensing means and said sensing means is controlled by the position of electrolyte within said delivery conduit.
 2. The apparatus of claim 1 wherein first and second mercury columns are positioned within said delivery conduit and an electrolyte is positioned between said mercury columns in said delivery conduit, said electrolyte and said mercury columns being in liquid-to-liquid interface engagement.
 3. The apparatus of claim 2 wherein said delivery tube is unwettable by said mercury and is wetted by said electrolyte so that said electrolyte maintains said mercury columns electrically separated except through said electrolyte.
 4. The apparatus of claim 3 wherein said electrolyte contains mercury ions in electrolyte solution.
 5. The apparatus of claim 1 wherein at least a portion of said delivery tube is substantially transparent and first and second columns of liquid mercury in said delivery tube are separated by a substantially transparent mercury plating electrolyte, said electrolyte being positioned between said electrodes.
 6. The apparatus of claim 5 wherein said sensor comprises a light source arranged to direct light through said delivery tube and a light sensor positioned to receive light passing from said light source through said delivery tube.
 7. The apparatus of claim 6 wherein said light source is a collimated light source and said sensor comprises first and second optical sensors positioned adjacent each other in a direction axial of said tube.
 8. A process for the controlled pumping of liquid mercury comprising the steps of: controllably admitting liquid mercury into a delivery tube so as to substantially fill the delivery tube; electrolyzing mercury across a mercury electrolyzing electrolyte which is positioned within the tube and separates the mercury column within the tube; and controlling the position of the electrolyte within the tube by controlling the admission of the liquid mercury into the tube.
 9. The process of claim 8 wherein said controlling step comprises: sensing the position of the electrolyte within the conduit; and controlling the admission of liquid mercury into the conduit by the sensed position of the electrolyte.
 10. The process of claim 9 wherein said sensing step comprises optically sensing the position of the electrolyte along the length of the conduit. 